Synthesis of [RuCl2(dppb)(PPh3)] and Identification of the cis- and trans-[RuCl2(dppb)(phen)] Geometrical Isomers via 31P{1H} NMR Spectroscopy. An Undergraduate Experiment for Inorganic Chemistry

A 31P{1H} NMR experiment for undergraduate students is presented involving the conversion of trans-[RuCl2(dppb)(phen)] to cis-[RuCl2(dppb)(phen)] (dppb = 1,4-bis(diphenylphosphino)butane; phen = 1,10-phenanthroline). This experiment (i) demonstrates the use of 31P{1H} NMR to distinguish between cis and trans geometric isomers of coordination compounds in solution, (ii) describes the concept of spin-spin coupling for P atoms by assigning signals to equivalent and nonequivalent P atoms, and (iii) offers an introduction to synthesis and in situ NMR work requiring semirigorous, inert-atmosphere conditions. The experiment can be accommodated in about four hours of laboratory time.